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SEM images of the samples. (a)Top view of a grating with converging slit wet etched on the free-standing Si wafer. (Inset: bottom view) (b) Oblique and (c) side view of the converging slit. (d) Side view of a CDC. (e)Top view of sample 1 with symmetrical CDC (period L = 350 μm, slit width a = 300 μm, b = 160 μm). (f) Top view of sample 2 with asymmetrical CDC (period L = 350 μm, a = 310 μm, b = 170 μm. A megascopic area in the dashed box is shown in the inset of Fig. 3 (a)), Scale bar: 200 μm.
(a) Zero-order transmission spectra of sample 1 (Black, red and blue solid are experimental results of Si, Au-Si, and Au-Au structures and green solid the simulation curve of PEC. Inset: Peak intensity of the (±1, 0) modefor different structures). (b-d) The angle-dependent transmission contour maps for PEC,Au-Au, and Si structures, respectively. Theoretical SPP bands (blue solid) are superposed on the maps, with different SPP modes indexed by (m, n).
(a) Zero-order transmission spectra of sample 2 (Inset: schematic plot of side view and SEM image of top view of a CDC with a shift s = 25 μm, cf. Fig. 1(f) ). Black, red, and blue solid lines are experimental results of Si, Au-Si and Au-Au sturctures; green solid is the simulation curve and purple solid the one without shift. (b) The simulated anti-resonance for different shifts (s = 5 ∼ 37.5 μm), the red dashed line represents the transmission maximum of sample without shift. (c) The modulation depth variation as a function of s.
(a) Simulated data (dot) and Fano fitting curve (red solid) of the (±1,0) mode for a grating with symmetric CDC which has the same geometrical parameter with sample 2. (b-d) , E x , and E z distribution at the resonant wavelength. The E y component is negligible compared to other components. (e) Simulated data (dot) and Fano fitting curve (red solid) of the anti-resonance for sample 2. (f-h) , E x and E z distribution at the anti-resonant dip (Unit: V/m).
(a) Simulated anti-resonance of sample 2 at different dielectric environment. (b) Resonant wavelength versus the RI of surrounding medium. The slope of the fitting curve shows the wavelength sensitivity. (c) Simulated anti-resonance for a small change of RI (0.05) of the surrounding medium. (d) Intensity change versus RI of surrounding medium at 378 μm. The slope of the fitting curve shows the intensity sensitivity.
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